The stir plates function is to keep the yeast in suspension. Yeast that settles out is not doing good work and the deeper in the pile, the less. This is why sparkling wine makers "riddle" their bottles and still winemakers "battonage" (stir up the lees). A yeast cake isn't getting much done, the more yeast in suspension, the better.
Something is always fermenting....
"It's Bahl Hornin'"
Kegged: Sour Saison, Pale Ale, Aggie Ale, Firestone DBA, De Koninck Blonde
Bottled: Belgian Quad (Grand Reserve), Derangement (Belgian Dark Strong)
On Deck: Pliny the Younger